Apparatus for the selective burning of different type gaseous fuels embodying a common burner element



Dec. 1, 1953 c A. REICHELDERFER 2,661,157

APPARATUS FOR THE SELECTIVE BURNING OF DIFFERENT TYPE GASEOUS FUELS EMBODYING A COMMON BURNER ELEMENT 2 Sheets-Sheet 1 Filed Nov. 15, 1950 Fl Ill.

ATTORNEY 1953 c. A. REICHELDERFER 2,661,157

APPARATUS FOR THE SELECTIVE BURNING OF DIFFERENT TYPE GASEOUS FUELS EMBODYING A COMMON BURNER ELEMENT Filed NOV. 15, 1950 2 Sheets-Sheet 2 INVENTOR C/Zaries 4 fea'ckeidezkr ATTORNEY Patented Dec. 1, 1953 2,661,157 APPARATUS FOR THE SELECTIVE BURNING DIFFERENT TYPE GASEOUS FUELS EMBODYING A COMMON BURNER ELE- MENT Charles A. Reichelderfer, Columbus, Ohio, assignor to Norman Products Company, Columbus, Ohio, a corporation of Ohio Application November 15, 1950, Serial No. 195,863

6 Claims. (01. 23691) The present invention relates to fuel-burning systems, and has particular reference to an improved fuel burner system adapted to selectively burn different types of gaseous fuels through a single burner head.

The use of gaseous fuel-burning systems for residential and industrial heating purposes has become increasingly popular in View of the increased availability of natural and/or manufactured municipally-supplied gases until, at the present time, practically all cities of higher population make available to individuals and companies gaseous fuel supplied through city or municipal mains. However, with the increased popularity of gaseous fuel-burning equipment, the consumption of such fuel has materially increased, particularly in relatively extreme cold weather periods. On such occasions, it is common that the supply of fuel within city or municipal mains is depleted to an extent that pressure within such mains falls to a degree rendering efiicient operation of the gas-burning equipment impossible. Further, the use of bottled or liquefied petroleum types of gaseous fuels has likewise become increasingly popular, due to the availability of such fuels and the heat-producing efficiency of the liquefied petroleum gases in comparison with natural or manufactured municipally supplied gaseous fuels.

However, it is Well known that different types of gaseous fuels require different amounts of air or oxygen to provide efiicient combustible mixtures for burning within domestic or industrial heating systems. For this reason, a given gaseous fuel burner must be provided with a primary air inlet of one size to effect the efficient burning of natural or manufactured gases or mixtures thereof, and a different sized primary air inlet opening for the burning of bottled or liquefied petroleum gas. In the past, it has been proposed to utilize in certain types of heating systems two separate burner heads and mixing chambers for the selective or simultaneous burning of both municipally-supplied gaseous fuels and bottled or liquefied petroleum gaseous fuels. It will be manifest that double systems of this type require unnecessary duplication of parts and machinery, and are consequently relatively expensive in manufacture, maintenance, and operation.

It follows. therefore, that the primary object of the present invention is to provide a burner system which employs but a single common burner head and mixing chamber and which is capable of efiiciently burning either municipallysupplied gaseous fuels or liquefied petroleum gaseous fuels without resorting to the use of a multiplicity of duplicate parts within the burner system.

It is another object of this invention to provide a burner system capable of burning a plurality of different types of gaseous fuels, and wherein provision is made for the automatic shifting from one type of gaseous fuel to another in response to the attainment of a predetermined low temperature within the atmosphere surrounding the building to be heated by the system, or in response to a predetermined decrease in the pressure of the supply of either type of gaseous fuel.

Still a further object of this invention is toprovide in a gaseous fuel burner system an electrical operating circuit which functions automatically in response to the temperature conditions of the zone heated by the burner to supply either municipal gaseous fuel or liquefied petroleum gaseous fuel to an associated common burner head, while at the same time auto matically varying the size of a primary air inlet opening associated with the burner head to vary the amount of primary air entering the mixing chamber of the burner in accordance with the amount of air required to produce an efficient combustible mixture with the particular type of gaseous fuel introduced to such burner head.

These and additional objects and advantages of the present invention will become more readily apparent by reference to the following description and the accompanying drawings, wherein:

Fig. 1 is a diagrammatic View of a multiple fuel-burning system forming the subject matter of the present invention; Fig. 2-is an enlarged vertical sectional view taken through the electro-responsive shutter associated with the-primary air intake opening of the fuel burner;

Fig. 3 is an enlarged fragmentary side elevational view of the shutter showing its relation to the primary air inlet of the burner; Fig. 4 is a diagram of a modified operating circuit for the present burner system wherein a shift from municipally-supplied gas to liquefied petroleum gas is eifected automatically in response to a predetermined decrease in the pressure of the gaseous fuel supplied through the municipal main; and

Fig. 5 is a similar view of still another modified operating circuit employed with the present burner system.

Referring now to the drawings-the numeral 10 designates a gaseous fuel burner head which ordinarily is positioned within the combustion chamber of a furnace or other heating instrumentality, not shown. The burner head Ill is provided with a tubular extension casing H which, internally, defines a mixing chamber in which gaseous fuels and primary combustion air are admixed to provide an efiicient combustible mixture prior to passage to the head l0. As shown diagrammatically in Fig. l of the drawings, the mixing chamber casing i.l communicates at its inner end with a pair of separate branch conduits l2 and I3 through which separate types of gaseous fuels may be introduced into the mixing chamber of the burner. The mixing chamber casing H is formed with an elongated primary air inlet slot M which extends a distance along the periphery of the casing l t and: through:

which primary air may pass for admixture with the gaseous fuel introduced within the chamber by way of either of the conduits l2 or I3. Preferably, the slot I4 is sized sothat when fully open the same will admit an excess amount of primary air over and above that necessary to providea maximum eiiiciency combustible mixture with a gaseous fuel of the liquefied. petroleum type- In this connection, it will. be' understood that any suitable adjustment means may be provided so as to adjust the size of: the slot l4 within limits in accordance with thesize' of opening necessary to provide the most efficient combustible mixture of a given type of gas; and air; Mounted. onthe outer surface of the casing; H, in the plane of. the slot 14, is: a slidable' shutter-type collar I15vv which is arranged for rotational movement upon the casing it within a: plurality of spaced guideforming brackets it. The shutter collar i5 is substantially arcuate ini its body region and terminates at one end in airadially and outwardly extending leg H. The opposite end of thershutter collar i5 is arranged to move over the slot It so that uponrelative rotation: of the collar upon the casing II the effective size of the primary air inlet slot 14' may be: varied to control the volume of air passing through the slot 14: for admixture with: fuel within the mixing chamber of the burner. The: radially extended leg I! of the collar is arranged so as to overbalance the collar in a manner to cause the same to close or partially restrict the slot 14' in response to the forces of gravity acting on the arm l1. Thus, the normal position of the: collar is such: as to decrease the normal size oi the: opening H to a degree to admit the proper amount of air necessary for the production of the most eflicient combustible mixtureof air and natural or manufactured gas. Toward this end, an adjustable limit stop, in the form" of a set screw [8, may be positioned below the extended leg I! of the shutter to adjust the degree of closing of the slot l4 by the shutter as the latter moves by gravity.

Positioned above and in vertical alignment with the extended leg I? of the shutter l5 -is an electromagnet l9 which, upon energization, serves to attract the leg llof the shutter in the manner of an armature to move the collar [5 in a counterclockwise direction as viewed Fig. 2 to increase the size of the air inlet slot I 4. As will hereinafter be more fully explained, the energization of the electromagnet I9, and the consequent opening of the slot [4 to a larger size, is accomplished automatically'in response to a shift from one type of gaseous fuel to another.

Turning now to the circuit diagram disclosed in Fig. 1 of the drawings, LI and L2 designate the main power lines which furnish operating current for the control system of the present dual fuel burner. Connected between the power lines LI and L2 is the. primary winding 20 of a transformer T. Connected with one pole of the secondary winding 2.l of the transformer T is a conductor 22. leading: to one.- pole of a. thermally responsive pilot safety switch 23. The pilot safety switch may be of any suitable construction and of a type normally employed in automatic burner control systems for the purpose of opening an operating circuit for the main fuel supply valve of the systemin response to the extinguishment of a pilot burner employed in igniting the main source of fuel at the burner head. Connected with the opposite: pole of the pilot safety switch 23 is a conductor-24 which leads to a movable arm or bimetal spiral 25 of a thermally responsive room thermostatic switch 26 of any suitable type. The switch 26 is provided with a stationary contact 2'! which is engaged by the bimetal spiral or movable arm 25. of. the switch in response to the attainment of a predetermined low temperature within a room or: zone to be heated by the burner, l0, Connected with the stationary contact 21 of the thermostat 26 is a lead wire 28 extending to and electrically connected with the movable arm or bimetal spiral 29 of a second three-way thermostatic switch 30. Preferably, the thermostatic switch 30 is positioned so as to be responsive to the temperature of the atmosphere outside of the: building, to be heated by the burner system, and is provided with spaced contact points 3i and; 32 arranged in the plane of movement. of the. bimetal. spiral. 29. Initially, the bimetal spiral 29 is arranged relative to the stationary' contact 31 so: asito engage the same during normally mild winter weather conditions in temperatures ranging, for example, upward from 30 F. The second stationary contact 32 is positioned relative to: the. bimetal spiral 29 so as to beengaged, by the spiral asthe temperature of the outside atmosphere drops below a predetermined level, say, for example, below 30 F. For purposes of illustration, the stationary contacts 3| and 32 have been; illustrated in relatively spaced relation, but it will be understood that in practice the contacts will: be relatively closely spaced. so' that the range of movement of the bimetal arm 29 is relatively slight in shifting between the two contacts.

Extending from and electrically connected with the stationary contact 31 of, the thermostat 30 is a conductor 33 leading to the winding 34a of. a solenoid-actuated. valve 34. The valve 34 is interposed within. the branch conduit 12 which is connected to. supply municipal main gas to the mixing chamber of the burner E8. The valve 34 is arranged to. normally close the conduit l2 to prevent the flow of fuel therethrough, and is energizable to open the same to permit free flow of fuel to the burner 13. The opposite side of the winding 34a is connected, by means of a lead 35, with the opposite pole of the secondary winding 2| of. the transformer T. Thus, upon engagement of the bimetal spiral 29 of the thermostat 30 with the stationary contact 3|, assum ing the thermostat 26 to be closed, as well as the pilot safety switch 23, an operating circuit is established for the winding of the solenoidactuated valve 34 to cause the same to open the conduit l2 to provide for the flow of municipal main gas, either manufactured or natural, within the mixing chamber of the burner i0.

Connected with the opposite stationary contact 32 of the switch 30 is a conductor 36 which branches, as at 31, into parallel circuit leads 38 and 39. The lead 39 is electrically connected with the winding 40 of a second solenoid-actuated valve 4| interposed within the conduit l3. The valve 4| is arranged to normally close the conduit |3 which is connected with a source of bottled or liquefied petroleum (LP) gaseous fuel, and thereby prevent the flow of LP gas through the conduit 13. However, upon energization of the winding 49, the valve 4| is opened to permit the free passage of LP gas into the mixing chamber of the burner 9. The opposite side of the winding 40 is connected by means of a lead 42 with a conductor 43 leading to the opposite side of the secondary winding 2| of the transformer T. The branch lead 39 is electrically connected with one side of the winding 44 of the electromagnet l9 which controls the movement of the shutter I 5, the opposite side of the winding 44 being con nected with the conductor 43 by means of a lead 55. Thus, upon engagement of the bimetal spiral 29 of the switch 39 with the stationary contact 32, parallel operating circuits are established for the windings 49 and 44 whereby the valve 4| is opened to permit passage of LP gas to the burner, while at the same time energizing the electromagnet l9 to attract the arm l! of the shutter l5 and move the latter to a position increasing the effective size of the slot M to admit a greater volume of air Within the mixing chamber of the burner ID in accordance with the demand for an eflicient combustible mixture of LP gas and air. It will here be understood that the thermostatic switch 30 serves to selectively or alternately close an operating circuit for either one or the other of the solenoid-actuated valves 34 or 4|, and due to the parallel circuit relation between the valve 4| and the electromagnet iii, the shutter I5 is automatically opened simultaneously with the opening of the LP gas valve 4 Upon deenergization of the valve 4|, by movement of the bimetal arm 29 into engagement with the stationary contact 3|, the electromagnet I9 is automatically deenergized, to permit the shutter |5 to move by gravity to its position decreasing the effective size of the slot M in accordance with the demand for primary air for admixture with municipally supplied gaseous fuel introduced by way of the conduit l2.

Fig. 4 of the drawings illustrates a modified control circuit wherein the selective energization of the solenoids associated with the separate valves 34 and 4| is controlled in response to the pressure of municipal main gas. In the diagram illustrated in Fig. 4, like elements of the circuit shown in Fig. I bear like reference numerals. The lead 28 extending from the stationary contact 2'! of the room thermostat 26 is electrically connected with a movable switch arm 4? which is pivoted, as at 48, to swing between a pair of relatively spaced contact terminals 49 and 50 connected respectively with the leads 39 and 33. One end of the switch arm 4! is connected, as at 5|, with an actuator rod 52 connected at its opposite end with a flexible pressure-responsive diaphragm 53 carried within a closed housing 54. Mounted between the housing 54 and the diaphragm 53 is a coil compression spring 55 which urges the diaphragm and the actuator rod 52 to move in a direction to swing, the switch arm 4? into engagement with the stationary contact 49. Under normal pressure conditions within the municipal main, the diaphragm 53 is flexed outwardly within the housing 54 to maintain the switch arm 4'! in engagement with the stationary contact 50, as

shown in Fig. 4, in opposition to the action of the spring 55. This outward fiexure of the diaphragm 53 is accomplished by the supply of gas pressure through a conduit 56 leading to the municipal gas main or to the conduit l2.

Thus it will be seen that the operating circuit disclosed in Fig. 4 normally provides for the burning of municipally-supplied gaseous fuels upon closure of the room thermostat 29. However, should the pressure of gas within the municipal main or conduit |2- drop below a predetermined level, the diaphragm-actuated switch arm 4'! automatically moves out of engagement with the stationary contact 59 and intoengagement with the opposite contact 49 to establish an operating circuit for the LP gas valve 4| and the electromagnet |9 which controls the opening of the shutter I5.

Fig. 5 of the drawings illustrates an operating circuit for the present dual fuel burner which is a composite of the circuits shown in Figs. 1 and 4, and wherein a shift from muncipally-supplied gaseous fuels to LP gas is effected in response to a predetermined decrease in the temperature of the outside atmosphere as well as in response to a decrease inthe pressure of fuel within the municipal main. Further, provision is made for the shifting from LP gas to municipal gas in response to a predetermined decrease in pressure within the supply of LP gas. In Fig. 5, like elements of the circuits shown in Figs. 1 and 4 bear like reference numerals. This operating circuit embodies the room thermostat 26 and the lead wire 28 extending to the outside air thermostat 39. Connected with the stationary terminal 3| of the outside air thermostat 39 is a lead 58 extending to and electrically connected with the switch arm 41 associated with the diaphragm-actuated switch which is connected with and responsive to the pressure within the municipal gas main. The contact 50 of the diaphragm-actuated switch is connected with the lead 33 extending to the winding 34a of the valve 34, the winding 34a being connected by the lead 35 with the opposite pole of the transformer T. The opposite contact 49 of the diaphragm-actuated switch is electrically joined with the conductor 36 which is connected at its opposite end with a contact 59 arranged to be engaged by the movable switch arm 60 associated with a second pressure-responsive switch. This second switch is identical to the pressure-responsive switch associated with the municipal gas supply, with the exception that the same is connected to be responsive to the pressure of the LP gas supply. Toward this end, the

inner end of the switch arm 69 is pivotally connected, as at 5|, with an actuator rod 32 extending outwardly from the diaphragm housing 33 and joined internally of the housing with a flexible diaphragm 64. The diaphragm chamberof the housing 63 communicates with a conduit 65 which is connected with the source of LP gas or with the conduit I3 at the inlet side of the valve 4!. The switch arm 60 is electrically connected with the stationary contact 32 of the outside air thermostat 30, as by means of the conductor 56.

mally provides for the admission of municipallysupplied gaseous fuels to the burner l0. Assuming the pilot safety switch 23 and the room thermostat 26 to occupy closed positions, the outside air thermostat 30 in relatively mild weather conditions has its bimetal spiral 29 in engagement with the stationary contact 3!. Assuming the pressure within the municipal main to be above or equal to an efficient operating level, the switch arm 4'! engages the stationary contact 58 to energize the winding 34a of the municipal gas valve 34 and thereby provide for the admission of municipally-supplied gas within the mixing chamber of the burner 10. However, should the temperature of the outside atmosphere fall below a predetermined low level, the outside air thermostat will engage the stationary contact 32 connected with the movable switch arm 60 of the second pressure-responsive switch associated with the LP gas supply; and assuming that the pressure of the LP gas supply is above or equal to an efficient operating pressure, the switch arm 80 will be held in engagement with the stationary contact 53 to complete an operating circuit for the LP gas valve 4! and the electromagnet H]. In the event that the pressure within the municipal main falls below a predetermined level, the switch arm 41 automatically moves out of engagement with the contact 50 and into engagement with the contact 38. Thus, if the temperature of the outside atmosphere remains above a predetermined low level, a shift circuit is established through the contact 3| of the outside air thermostat 39, the switch arm 41, the stationary contact 49, and to the LP gas valve and electromagnet to moves into engagement with the contact 61 to an provide a bypass circuit by way of the conductor 68 to energize the municipal gas valve 34. This latter shift is possible only when the temperature of the outside atmosphere is below the predetermined low level and when the switch arm 29 of the outside air thermostat is in engagement with the stationary contact 32. It should be understood that the circuit disclosed in Fig. is designed to provide an automatic shift from municipally-supplied gas to LP gas under mild weather conditions in response to a decrease in pressure in the municipal gas main, while a shift from LP gas to municipal gas under relatively extreme low temperature conditions is effected in response to a predetermined drop in the pressure of the LP gas supply. In this manner, continuous operation of the burner is assured, assuming that the pressure of the municipally-supplied gas does not fail, altogether.

In view of the foregoing, it will be seen that the present invention provides a burner system capable of the efiicient burning of a plurality of different types of gaseous fuels, wherein such different types of fuels require different quantities of primary air to provide for the most efiicient burning or" such fuels. As before mentioned, the size of the primary air inlet associated with the fuel burner may be established or adjusted by any suitable means in accordance with the known limits of operation with particular types of gaseous fuels. Thereafter, the electro-responsive shutter functions to vary the-size of the primary air inlet in accordance with the particular type of gaseous fuel introduced for burning within the burner. The operating circuits associated with the present system provide for the automatic shifting from one type of gaseous fuel to another and a consequent variance in the size of the primary air inlet of the burner in response to varying conditions of temperature and fuel availability.

I claim:

1. In a gaseous fuel burner system; a single burner for gaseous fuels; primary air inlet means on said burner arranged to admit air into gaseous fuels introduced to said burner for admixture with such fuels prior to combustion; a first conduit connected to supply a first type of gaseous fuel to said burner; a second conduit connected to supply a second type of gaseous fuel to said burner; shutter means arranged adjacent to said primary air inlet means and movable to vary the effective size of said inlet means and thereby to vary the volume of primary air passing inwardly of said burner; electro-responsive means energizable to move said shutter means; normally closed electrically actuated valve means connected with each of said first and second conduits and energizable to open said conduits to permit the free flow of fuels therethrough; and switch means having electrical connections with said electro-responsive means and said electrically actuated valve means and operable to alternately close operating circuits for said electro-responsive means and the valve means connected with one of said conduits while opening a circuit for the valve means connected with the other of said conduits or for closing an operating circuit for said last-named valve means while opening operating circuits for said electro-responsive means and said first-named valve means.

2. In a heating system fired by two different types of gaseous fuels; 2. single fuel burner having a fuel-air mixing chamber; primary air inlet means communicating directly with the mixing chamber of said burner for admitting primary air to said chamber; a first fuel supply conduit connected between the chamber of said burner and a first source of gaseous fuel; a second fuel supply conduit connected between the mixing chamber of said burner and a second source of gaseous fuel; electrically actuated valve means normally closing each of said supply conduits and energizable to open the latter to permit the free flow of fuel through said conduits and to said burner; switch means having electrical connections with said valve means and operable to close an operating circuit for the valve means of either of said conduits while opening an operating circuit for the valve means of the other of said conduits; and electro-responsive shutter means disposed adjacent to said primary air inlet means and electrically connected with said switch means and movable, in response to the operation of said switch means, to vary the effective size of said inlet means and thereby to vary the amount of primary air admitted to said chamber in accordance with the type of gaseous fuel introduced to said burner.

3. In a fuel burner system adapted for the selective burning of a plurality of different types of gaseous fuels requiring varying quantities of primary air for maximum efiiciency in burning; a single fuel burner provided with an air-gas mixing chamber; primary air inlet means communicating directly with the mixing chamber for admitting primary air thereto; electro-re sponsive means movable to vary the effective size of said air inlet means and thereby to vary the volume of primary air entering said chamber; a

first fuel supply conduit arranged to introduce a first type of gaseous fuel to the mixing chamber of said burner; a second fuel supply conduit arranged to introduce a second type of gaseous fuel to the mixing chamber of said burner; electrically-actuated valves interposed within each of said first and second conduits for controlling the passage of fuels therethrough, said valves being normally closed but energizable to open said conduits to permit free fiow of fuels therethrough; and switch means having electrical connections with each of said valves and with said electro-responsive means and operable to simultaneously control the energization of said valves and the movement of said electroresponsive means, whereby to vary the effective size of said air inlet means in accordance with the type of fuel being introduced to said fuel burner by way of said conduits.

4:. In a fuel burner system for the selective burning of a plurality of different types of gaseous fuels requiring varying quantities of primary air for maximum efiiciency in burning; a single fuel burner; primary air inlet means in said burner arranged to admit air for admixture with fuels prior to burning thereof at said burner; electro-responsive means associated with said primary air inlet means and movable to vary the effective size of the latter and thereby to control the quantity of air to be admitted through said air inlet means for admixture with fuels introduced to said burner; a first fuel supply conduit connected between a first source of gaseous fuel and said burner; a second fuel supply conduit connected between said burner and a second source of gaseous fuel of a type different from the gaseous fuel of said first source; electrically-actuated valves interposed within each of said first and second conduits between said sources and said burner for controlling the passage of fuels to said burner, said valves being movable between positions opening and closing said conduits; and switch means electrically connected in an operating circuit for said valves and said electro-responsive means and operable alternately to energize one of said valves while deenergizing the other and to control the energization of said electro-responsive means to provide for an automatic variance in the effective size of said primary air inlet means in accordance with the type of gaseous fuel introduced to said burner.

5. In a fuel burner system adapted for the selective burning of a plurality of different types of gaseous fuels each requiring varying amounts of primary air for maximum efiiciency in burning; a single gaseous fuel burner provided with a primary air inlet opening for admitting air to the burner for admixture with gaseous fuels introduced thereto prior to combustion; shutter means movable to vary the effective size of the primary air inlet opening and thereby control the amount of primary air introduced to said burner by way of said opening; electro-responsive mean for controlling the movement of said shutter means; a first fuel supply conduit connected between a first source of gaseous fuel and said burner; a second fuel supply conduit connected between said burner and a second source of gaseous fuel of a type different from the gaseous fuel of said first source; electrically-actuated valves interposed within each of said first and second conduits for controlling the fiow of fuel through said conduits and to said burner; and switch means having electrical connections with each of said valves and said electro-responsive means and responsive to a predetermined decrease in the pressure of fuel in either of said conduits for establishing an operating circuit for the valve of the other of said conduits and for controlling the operation of said electroresponsive means to provide for a variation in the eifective size of the primary air inlet opening of said burner.

6. In a fuel burner system adapted for the selective burning of a plurality of different types of gaseous fuels each requiring varying amounts of primary air for maximum eificiency in burning; a single gaseous fuel burner provided with a primary air inlet opening for admitting air to the burner for admixture with gaseous fuels introduced thereto prior to combustion; shutter means movable to vary the effective size of the primary air inlet opening and thereby control the amount of primary air introduced to said burner by way of said opening; electro-responsive means for controlling the movement of said shutter means; a first fuel supply conduit connected between a first source of gaseous fuel and said burner; a second fuel supply conduit connected between said burner and a second source of gaseous fuel of a type different from the gaseous fuel of said first source; electrically-actuated valves interposed within each of said first and second conduits for controlling the flow of fuel through said conduits and to said burner; and switch means electrically connected with said valves and said electro-esponsive means and responsive to either a change in the temperature of the outside atmosphere or to a predetermined decrease in pressure of fuel in either of said conduits for opening an operating circuit for one of said valves while closing an operating circuit for the other of said valves and for alternately opening or closing an operating circuit for said electro-responsive means to thereby vary the effective size of the primary air inlet opening of said burner in accordance with the type of gaseous fuel to be introduced to said burner.

CHARLES A. REICHELDERFER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,786,900 Doherty Dec. 30, 1930 1,839,977 Lobbecke Jan. 5, 1932 1,840,744 Scott Jan. 12, 1932 2,293,550 Kells Aug. 18, 1942 2,547,611 Young Apr. 3, 1951 2,552,302 Young May 8, 1951 2,582,582 Bottom Jan. 15, 1952 FOREIGN PATENTS Number Country Date 454,982 Great Britain Oct. 12, 1936 838,128 France Feb. 28. 193 

